Fix RUF100 to detect unused file-level noqa directives with specific codes (#17042) (#17061)
Closes #17042
## Summary
This PR fixes the issue outlined in #17042 where RUF100 (unused-noqa)
fails to detect unused file-level noqa directives (`# ruff: noqa` or `#
ruff: noqa: {code}`).
The issue stems from two underlying causes:
1. For blanket file-level directives (`# ruff: noqa`), there's a
circular dependency: the directive exempts all rules including RUF100
itself, which prevents checking for usage. This isn't changed by this
PR. I would argue it is intendend behavior - a blanket `# ruff: noqa`
directive should exempt all rules including RUF100 itself.
2. For code-specific file-level directives (e.g. `# ruff: noqa: F841`),
the handling was missing in the `check_noqa` function. This is added in
this PR.
## Notes
- For file-level directives, the `matches` array is pre-populated with
the specified codes during parsing, unlike line-level directives which
only populate their `matches` array when actually suppressing
diagnostics. This difference requires the somewhat clunky handling of
both cases. I would appreciate guidance on a cleaner design :)
- A more fundamental solution would be to change how file-level
directives initialize the `matches` array in
`FileNoqaDirectives::extract()`, but that requires more substantial
changes as it breaks existing functionality. I suspect discussions in
#16483 are relevant for this.
## Test Plan
- Local verification
- Added a test case and fixture
ruff
f1d4ba32 - Fix RUF100 to detect unused file-level noqa directives with specific codes (#17042) (#17061)
